Epstein Barr Virus (EBV)-associated lymphoma remains a major problem among AIDS patients, and Kaposis sarcoma, which has declined in frequency in recent years, can still cause debilitating disease in HIV-infected patients. In collaboration with Peter Burbelo, we are examining antibody responses to EBV and HHV-8 in patients who develop either lymphoma (EBV) or Kaposis sarcoma (HHV-8), using a new technology developed by Dr. Burbelo, the luciferase immunoprecipitation system (LIPS), which allows rapid detection of antibodies over a broad dynamic range. For HHV-8, our goal is to see if we can develop a better diagnostic assay for HHV-8 infection, as there is no FDA-approved assay for this infection. Our preliminary results have shown that a mixture of 4 antigens in the LIPS assay performs at least as well as an ELISA-based assay. For EBV, we are examining the relationship between development of lymphoma and changes in antibody titers to EBV-specific proteins, as well as EBV viral load and EBV-specific immune responses. Our data so far suggest that there is no relationship between anti-EBV antibody titers and development of lymphoma. The remaining assays have not yet been performed. Both HIV infection and antiretroviral nucleoside analogues (nucleoside reverse transcriptase inhibitors or NRTIs) are known to affect mitochondrial DNA content and mitochondrial function. A number of important clinical syndromes observed in HIV-infected persons relate to mitochondrial dysfunction including lactic acidosis, myopathy, cardiomyopathy, pancreatitis, peripheral neuropathy, and possibly lipodystrophy 1, 2. Fatigue, one of the most prevalent complaints among persons with HIV infection, may also be the result of mitochondrial toxicity, though this has not been clearly established. Availability of minimally invasive tests to assess mitochondrial toxicity would greatly facilitate understanding of the contribution of mitochondrial dysfunction to clinical syndromes. Muscle and liver biopsies are currently considered to be the reference standards for the evaluation and diagnosis of mitochondrial toxicity in muscle and liver, but these invasive tests are impractical for routine and repeated evaluations. The recent development of a real-time polymerase chain reaction (PCR) assay to accurately quantify the mtDNA copy numbers per cell in peripheral blood mononuclear cells (PBMCs) may allow non-invasive assessment of mitochondrial toxicity. We have undertaken a pilot study seekings to examine the relationship between fatigue and other clinical parameters and markers of mitochondrial dysfunction. The goals of this study are threefold: 1) to investigate the relationship between subjective fatigue ratings and mitochondrial dysfunction through measurements of mtDNA depletion in skeletal muscle 2) to determine whether there is a relationship between evidence of mitochondrial dysfunction in muscle and evidence of mitochondrial dysfunction in lymphocytes or adipose tissue suggesting that examination of lymphocytes or adipose tissue may be adequate for the accurate diagnosis of mitochondrial dysfunction and 3) to identify genes and proteins as potential biomarkers for fatigue and mitochondrial toxicity. This study has completed enrollment and we are currently in the process of analyzing the data. At present, there are no clear guidelines as to when antiretroviral (ARV) therapy for human immunodeficiency virus (HIV) should be stopped in the setting of elevated liver enzymes. In large part, this is due to a limited understanding of the natural history of ARV-related hepatotoxicity. We have undertaken a pilot study to estimate the prevalence of hepatic fibrosis in a cohort of sixty HIV-infected patients who have chronically elevated transaminases while on ARV therapy in the absence of Hepatitis B (HBV) or C (HCV) coinfection. Liver biopsy specimens will be evaluated for fibrosis by microscopic examination, the current gold standard for assessing the nature and severity of liver disease. Fibrosis, as well as other histopathology, will be measured using a validated scoring system. To date, about 30 patients have enrolled in the study and have undergone liver biopsy. Significant liver abnormalities, primarily steatohepatitis, but also fibrosis, have been seen in the majority of patients. This study should provide clinically relevant information on the significance of elevated transaminases in HIV-infected patients without co-infection with HCV or HBV.